Magnetically guided exercise devices and systems

ABSTRACT

A strength training apparatus comprises a frame. In addition, the strength training apparatus comprises an elongate guide member including a magnet. Further, the strength training apparatus comprises a weight plate including a guide bore through which the guide member is disposed that includes a magnet corresponding to the magnet of the guide member. The magnet of the guide bore and the magnet of the guide member are oriented to produce repulsive magnetic forces between the weight plate and the guide member.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. provisional application Ser. No. 60/870,983 filed Dec. 20, 2006, and entitled “Magnetically Guided Exercise Devices and Systems,” which is hereby incorporated herein by reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND

Proper exercise and weight training have long been recognized as beneficial for improving cardiovascular health as well as strength. Most individuals weight train in local gyms or exercise clubs that provide access to a variety of conventional weight lifting machines, such as Nautilus® and Cybex® type machines. Most of these conventional weight lifting machines comprise a relatively rigid frame, a pulley system, and a vertical stack of weight plates. The frame typically includes two parallel vertical guide rods that each pass through a vertical bore formed in the stack of weights. The guide rods generally maintain the vertical orientation of the stack of weight plates and guide the vertical motion of one or more of the individual weight plates during use of the machine. In most cases, a vertically oriented weight selection bar coupled to the pulley system also passes vertically through the central portion of the stack of weights and is manually coupled to one or more of the weight plates, typically by a pin. The user of the machine can select the desired amount of total weight to be lifted by manually changing the location of the pin, thereby increasing or decreasing the number of weight plates, and hence, the total amount of weight, coupled to the weight selection bar. With the desired amount of weight coupled to the weight selection bar, the user exerts a force through the pulley system to either raise the one or more weight plates coupled to the weight selection bar against gravity. As the weights are lifted by the user they move vertically relative to the guide rods, their vertical motion controlled and guided the guide rods.

Most conventional weight lifting machines also include mechanical bushings positioned between the stack of weight plates and one or both guide rods. The mechanical bushings, which may be roller-type bushings, are intended to reduce frictional forces between the moving weight plates and the guide rods and enable smooth operation of the weight machine. However, since these mechanical bushings physically contact one or more guide rods, some frictional forces inevitably arise the interface between the bushings and the guide rods, even if the guide rods are polished smooth. Such friction and wear the bushings and guide rods over time. Further, as the guide rods and bushings get dirty, the friction between the bushings and guide rods tends to increase due to an increase in the coefficient of friction therebetween.

Inadequate and/or dirty bushings may cause abrupt and unpredictable movement of the weights being lifted, which may result in injury to the user. For instance, if a bushing sticks, the user may begin to exert a greater force on the pulley system until the bushing suddenly “breaks free”, resulting in an abrupt movement or jerk of the weights. In addition, a failure of one of these bushings may result in an undesired effective increase in the total amount of weight being lifted by the user. For example, frictional forces between a bad bushing and a guide rod will act against the relative motion therebetween, thereby increasing the overall resistance the user must overcome to lift the weight.

To ensure the mechanical bushings between the weight plates and guide rods are working properly, regular inspection and maintenance is often required. For instance, periodically, the bushings must be visually inspected and repaired if necessary. In addition, the bushings and guide rods may need periodic cleaning to ensure a smooth sliding contact between the bushings and guide rods, and to reduce the buildup of dirt or other contaminants which could reduce the effectiveness of the bushings over time. In some gyms and health clubs that have twenty, thirty, fifty or more weight machines, the daily maintenance and cleaning of bushings and guide rods can take up a significant amount of time and effort.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed description of the embodiments of the invention, reference will now be made to the accompanying drawings in which:

FIG. 1 is a front view of an embodiment of a strength training machine constructed in accordance with the principles described herein;

FIG. 2 is a side view of the strength training machine of FIG. 1;

FIG. 3 is a partial enlarged front view of the stack of weight plates and guide members of the strength training machine of FIG. 1;

FIG. 4 is a cross-sectional view taken along line 2-2 of FIG. 3;

FIG. 5 is a partial enlarged front view of an embodiment of a strength training machine constructed in accordance with the principles described herein; and

FIG. 6 is a cross-sectional view taken along line 3-3 of FIG. 5.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The following discussion is directed to various embodiments of the invention. The embodiments disclosed should not be interpreted, or otherwise used, as limiting the scope of the disclosure, including the claims. In addition, one skilled in the art will understand that the following description has broad application, and the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to intimate that the scope of the disclosure, including the claims, is limited to that embodiment.

Certain terms are used throughout the following description and claims to refer to particular features or components. As one skilled in the art will appreciate, different persons may refer to the same feature or component by different names. This document does not intend to distinguish between components or features that differ in name but not function. The drawing figures are not necessarily to scale. Certain features and components herein may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in interest of clarity and conciseness.

In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . .” Also, the term “couple” or “couples” is intended to mean either an indirect or direct connection. Thus, if a first device couples to a second device, that connection may be through a direct connection, or through an indirect connection via other devices and connections.

Referring to FIGS. 1-3, a strength or weight training machine 10 is illustrated. Machine 10 includes a rigid frame 20 that supports a pulley system 30, a mounting apparatus 45, and a plurality of weight plates 51 forming a weight stack 50. Pulley system 30 includes pulleys 32 rotationally coupled to frame 20 and a cable 35 that passes over and is guided by pulleys 32. Cable 35 has a first end 35 a coupled to a user interface member 40 and a second end 35 b coupled to a weight selection bar 70. In general, user interface member 40 is the structure manipulated by the user of machine 10 for strength training. In this embodiment, user interface member 40 is a rigid bar that is pulled by the user of machine 10, however, in general, the user interface member (e.g., user interface member 40) may comprise any suitable device that is manipulated (e.g., pushed, pulled, rotated, etc.) by an individual using the weight training machine (e.g., machine 10).

Weight selection bar 70 is an elongate member slidingly received in a generally mating selection bar bore 71 that passes generally through the center of weight stack 50. Weight selection bar 70 is coupled, usually by a pin, to one or more individual weight plates 51. By adjusting the number of individual weight plates 51 coupled to weight selection bar 70, the user can select the desired amount of total weight to be lifted. In addition, two guide member bores 61 are provided through weight stack 50 to slidingly receive guide bars or members 60. The ends of each guide member are fixed to frame 20.

Guide members 60 substantially maintain the orientation of weight stack 50 and serve to guide the motion of one or more individual weight plates 51 coupled to weight selection bar 70. In particular, during use, an individual will generally select a desired weight resistance by coupling a desired number of weight plates 51 to weight selection bar 70. This is usually accomplished manually with a pin. With the user properly positioned in mounting structure 45, the used grasps user interface member 40 and pulls (or pushes depending on the weight machine) on interface member 40. Interface member 40 is coupled to the desired amount of weight coupled to weight selection bar 70 via cable 35. Thus, the force applied by the user to interface member 40 is translated through cable 35 and weight selection bar 70 to the individual weight plates 51 coupled to weight selection bar 70. If this force is sufficient, cable 35, weight selection bar 70, and the individual weight plates 51 coupled to weight selection bar 70 will be lifted. As the individual weight plates 51 move relative to frame 20, guide members 60 maintain the orientation of individual weight plates 51 and generally guide their motion.

Referring now to FIGS. 3 and 4, the user couples one or more weight plates 51 to weight selection bar 70 to achieve the desired total amount of weight to be lifted. In this embodiment, the user slides a pin (not shown) through an aperture 73 in a specific weight plate 51, termed the “pinned” weight plate 51, and through a mating pin bore 74 in weight selection bar 70 that is aligned with aperture 73. Once the pin is sufficiently inserted through aperture 73 and mating pin bore 74, the pinned weight plate 51 and each weight plate 51 disposed above the pinned weight plate 51 is coupled to weight selection bar 70. During use of machine 10, each weight plate 51 coupled to weight selection bar 70 moves relative to frame 20 and guide members 60, with the motion generally guided by guide members 60.

As best shown in FIG. 4, each weight plate 51 includes two guide member bores 61 a that each slidingly receives a guide member 60 and a selection bar bore 71 a that slidingly receives weight selection bar 70. In this embodiment, guide member bores 61 a are generally disposed proximal opposite ends of weight plate 51, and select bar bore 71 a is disposed at the center of weight plate 51. However, it should be appreciated that the bores may also be located in other positions within the weight plates 51. Individual weight plates 51 are stacked and oriented such that bores 61 a, 71 a provided in each individual weight plate 51 are aligned, thereby defining bores 61, 71, respectively, through weight stack 50.

Referring specifically to FIG. 4, each individual weight plate 51 also includes a plurality of plate magnetic inserts 80 disposed in mating recesses 81 provided in each weight plate 51. In this embodiment, four recesses 81 are equally angularly spaced about 90° apart along the inner surface of each guide member bore 61 a. However, in general, one or more recess (e.g., recesses 81) and plate magnetic inserts (e.g., plate magnetic inserts 80) may be provided along the inner surface of each guide member bore (e.g., guide member bore 61 a) at any suitable location(s). In some embodiments, the plate magnetic inserts may not be disposed in recesses. In still other embodiments, the entire inner surface of the guide member bore may comprise a plate magnetic insert.

Referring still to FIG. 4, each guide member 60 includes a plurality of guide magnetic inserts 90 disposed in mating recesses 91 provided in the outer surface of each guide member 60 throughout the range of travel of the weight plates 51. In this embodiment, four recesses 91 are equally spaced approximately 90° apart around the outer surface of each guide member 60. However, in general, one or more recess (e.g., recesses 91) and guide magnetic inserts (e.g., guide magnetic inserts 90) may be provided along the outer surface of each guide member (e.g., guide member 60) at any suitable location(s). In some embodiments, the guide magnetic inserts may not be disposed in recesses. In still other embodiments, the entire outer surface of the guide member may comprise a plate magnetic insert.

Magnetic inserts 80, 90 may be secured to each weight plate 51 and guide member 60 by any suitable means including, without limitation, an interference fit with recesses 81, 91, respectively, adhesives, a welded connection, or combinations thereof. In addition, recesses 81, 91 may be molded or cast, as part of each weight plate 51 and each guide member 60, respectively, or machined from each weight plate 51 and guide member 60, respectively. In other embodiments, the magnetic inserts (e.g., magnetic inserts 80, 90) may be integral with each weight plate and/or each guide member.

Referring still to FIG. 4, each guide magnetic insert 90 is positioned substantially opposite and facing a corresponding plate magnetic insert 80. Thus, for each guide magnetic insert 90 in the outer surface of each guide member 60, there is a corresponding plate magnetic insert 80 provided in the inner surface of each guide member bore 61. However, magnetic inserts 80, 90 are radially spaced apart by an annulus or gap 85 positioned between each weight plate 51 and each guide member 60. Specifically, each guide member bore 61 a has a radius R₁ defined by the inner surface of each guide member bore 61 a, and each guide member 60 has a radius R₂ defined by the outer surface of each guide member 60, where radius R₁ is greater than radius R₂, resulting in gap 85.

Magnetic inserts 80, 90 are oriented such that the common poles of magnetic inserts 80, 90 face each other across gap 85, resulting in repulsive magnetic forces between magnetic inserts 80, 90. The repulsion between magnetic inserts 80, 90 and the positioning of the magnetic inserts throughout the range of travel of the weight plates 51 offers the potential to maintain gap 85 and the physical separation of each weight plate 51 and each guide member 60 as each weight plate 51 moves relative to guide members 60, while still allowing guide members 60 to guide the movement of each weight plate 51. The potential to maintain the physical separation of each guide member 60 and each weight plate 51, also enables reduced contact and associated friction between weight plates 51 and guide members 60, thereby offering the potential for relatively consistent, smooth motion of weight plates 51 relative to frame 20 and guide members 60. Such a configuration employing magnetic inserts (e.g., magnetic inserts 80, 90) in the guide members (e.g., in guide members 60) and in the individual weight plates (e.g., in each weight plates 51) to maintain physical separation of the guide members and the weight plates may be termed herein as a “magnetic bushing.”

The “magnetic bushings” disclosed herein offer the potential to provide low friction, relatively smooth movement of weight plates 51 relative to guide members 60. In particular, since magnetic inserts 80, 90 operate to maintain gap 85 between weight plates 51 and guide members 60, contact between weight plates 51 and guide members 60 is substantially reduced, thereby significantly reducing friction therebetween. Further, although the outer surface of guide members 60 and inner surface of guide member bores 61 are preferably smooth and clean, since repulsive magnetic forces are not noticeably inhibited by slight to moderate dirt buildup, the time and effort spent cleaning guide members 60 and/or weight plates 51 may be reduced as compared to conventional weight lifting machines, potentially saving time and money.

Referring now to FIGS. 5 and 6, a second embodiment of a strength or weight training machine 100 is illustrated. Machine 100 includes a frame 120, guide members 160, and a weight stack 150 including a plurality of individual weight plates 151. Machine 100 is operated substantially the same as machine 10 previously described. Namely, the user of machine 100 selects the desired amount of weight to be lifted by coupling one or more weight plates 151 to weight selection bar 170 with a pin (not shown). In this embodiment, the user slides the pin through an aperture 173 in a particular individual weight plate 151, termed the “pinned” weight plate 151, and through a mating pin bore 174 provided in weight selection bar 170. Once the pin is sufficiently inserted through aperture 173 and mating pin bore 174, the pinned weight plate 151 and each weight plate 151 disposed above the pinned weight plate 151 move with weight selection bar 170. In particular, each weight plate 151 coupled to weight selection bar 170 moves relative to frame 120 and guide members 160, the motion guided by guide members 160. However, in this embodiment, guide members 160 are not disposed through each weight plate 151.

As best shown in FIG. 6, in this embodiment, each guide member 160 includes a generally L-shaped cross section having an inside or stack facing surface 160 a and an outer surface 160 b generally opposite surface 160 a. In addition, each guide member 160 is positioned a corner 152 of stack 150 and each weight plate 151. Although stack facing surface 160 a of each guide member 160 faces weight stack 150, it does not contact any of weight plates 151. Rather, stack facing surface 160 a is slightly spaced apart from corner 152 by a gap 185 therebetween. Guide members 160 serve to substantially maintain the orientation of stack 150 and substantially guide the movement of weight plates 151. More specifically, together, the plurality of guide members 160 form a structure within which stack 150 of weight plates 151 is maintained. Unlike guide members 60 illustrated in FIGS. 3 and 4, guide members 160 shown in FIGS. 5 and 6 are not disposed through each weight plate 151, but rather are positioned about the outer corners 152 of the stack 150 of weight plates 151. Although four guide members 160 are shown in FIG. 6, one generally at each corner 152, in general, any suitable number and location of guide members (e.g., guide members 160) may be employed.

Referring still to FIG. 6, each weight plate 151 includes a selection bar bore 171 a that together define a selection bar bore 171 through the entire weight stack 150 that slidingly receives weight selection bar 170. Each weight plate 151 also includes a plurality of plate magnetic inserts 180 disposed in recesses 181. Recesses 181, and hence plate magnetic inserts 180, are positioned generally at each outer corner 152 of each weight plate 151. Specifically, a recess 181, including a plate magnetic insert 180, is placed along the outside surface of each side of weight plate 150 adjacent each outer corner 152. In this particular embodiment, two recess 181 are positioned along the outside surface of each side of weight plate 151, resulting in eight recesses 181, each accommodating a plate magnetic insert 180. However, in general, any suitable number and location of the plate magnetic inserts (e.g., plate magnetic inserts 180) may be provided along the outside surface of one or more sides of the weight plates (e.g., weight plates 151).

In addition, each guide member 160 includes a plurality of guide magnetic inserts 190 disposed throughout the range of travel of the weight plates 150 in recesses 191 provided in stack facing surface 160 a of each guide member 160. The magnetic inserts 190 may be each be one piece that covers the range of travel or may be multiple pieces spaced over the range of travel. In this particular embodiment, one recess 191, accommodating one guide magnetic insert 190, is disposed in each leg of each L-shaped guide member 160, resulting in two recesses 191 and two guide magnetic inserts 190 for each guide member 160.

Magnetic inserts 180, 190 may be secured within recesses 181, 191, respectively, by any suitable means including without limitation press fitting, adhesives, weld bead, or combinations thereof. In addition, recesses 181, 191 may be formed by molding or casting as part of each weight plate 151 and each guide member 160, respectively, or machined from each weight plate 151 and guide member 160. Magnetic inserts 180, 190 may also be integral with each weight plate 151 and guide member 160, respectively. Additionally, magnetic inserts 180, 190 do not need to be disposed in recesses.

Referring still to FIG. 6, each guide magnetic insert 190 is generally positioned immediately opposite and facing a corresponding plate magnetic insert 180. Thus, there is one guide magnetic insert 190 in stack facing surface 160 a for each guide member 160 for each plate magnetic insert 180 provided on the outer surface of each weight plate 151 adjacent corner 152. However, magnetic inserts 180, 190 are spaced apart by gap 185. In addition, magnetic inserts 180, 190 are oriented within recesses 181, 191 such that common poles in magnetic inserts 180, 190 face each other across gap 185, resulting in repulsive magnetic forces between magnetic inserts 180, 190. The repulsion between magnetic inserts 180, 190 tends to maintain gap 185, even as each weight plate 151 coupled to weight selection bar 170 moves relative to guide members 160 and frame 120.

Still referring to FIGS. 5 and 6, as each weight plate 151 coupled to weight selection bar 170 moves during use of machine 100, repulsive forces between magnetic inserts 180, 190 tend to maintain physical separation of each guide member 160 and each weight plate 151, thereby reducing contact and resulting friction between weight plates 151 and guide members 160. As a result, weight plates 151 tend to exhibit relatively consistent, stable, smooth motion relative to frame 20 and guide members 160 during use of Machine 100. Thus, this configuration of repelling magnetic inserts 180, 190 in guide members 160 and in weight plates 151 may also be termed a “magnetic bushing.”

The use of the “magnetic bushings” disclosed herein offer the potential to provide low friction, relatively smooth movement of weight plates 151 relative to guide members 160. In particular, since magnetic inserts 180, 190 operate to substantially maintain gap 185 between weight plates 151 and guide members 160, contact between weight plates 151 and guide members 160 is substantially reduced, thereby significantly reducing friction therebetween. Further, although stack facing surface of guide members 160 and the outer surface of corners 152 of each weight plate 151 are preferably smooth and clean, since repulsive magnetic forces are not noticeably inhibited by slight to moderate dirt buildup, the time and effort spent cleaning guide members 160 and/or weight plates 151 may be reduced as compared to conventional weight lifting machines, potentially saving time and money.

In some embodiments, guide members 60 passing through guide bores 61 in each weight plate 51 (FIG. 4) and guide members 160 positioned adjacent each corner 152 of each weight plate 151 (FIG. 6) may both be incorporated into a single weight machine. In such embodiments, magnetic inserts 80, 180 in each weight plate and magnetic inserts 90, 190 in each guide member work together to substantially maintain the orientation of the weight stack and to reduce contact and friction between the weight stack and guide members 60, 160.

Magnetic inserts 80, 180, 90, 190 may comprise any suitable magnetic material, including without limitation neodymium, iron, or the like. Alternatively, inserts 80, 180, 90, 190 may comprise electromagnets.

Although the embodiments illustrated herein shown magnetic inserts 80, 180 disposed in recesses 81, 181 in each weight plate 51, 151, respectively, and magnetic inserts 90, 190 disposed in recesses 91, 191 in each guide member 60, 160, respectively, alternatively, each weight plate and guide member may be formed from a magnetic material, or material capable of being electro-magnetized, thereby eliminating the need for distinct magnetic inserts and recesses. For instance, referring to FIG. 7, an individual weight plate 251 includes a magnetic material (or a material capable of being electro-magnetized), and two guide members 260 formed from a magnetic material, or comprise electromagnets, thereby eliminating the need for distinct magnetic inserts. The embodiment illustrated in FIG. 7 operates substantially the same as the embodiment illustrated in FIG. 6. The repulsive magnetic forces between weight plate 251 and guide members 260 substantially maintaining gap 285 and the orientation of weight plate 251 relative to guide members 260.

In the manner described, embodiments described herein offer the potential to reduce physical contact and associated friction between the individual weight plates (e.g., weight plates 51, 151) and the guide members (e.g., guide members 60, 160) that maintain the orientation of the weight plates and guide the movement of the weight plates. In particular, embodiments described herein utilize magnetic repulsion forces to substantially maintain the physical separation between the weight plates and the guide members. As a result, the embodiments described herein offer the potential for weight machines including magnetic bushings which require less maintenance, while enabling relatively stable smooth movements during use.

It should be appreciated that machine 10 illustrated in FIGS. 1 and 2 is an exemplary weight lifting machine that includes a stack of weight plates. In particular, machine 10 is a lat pull-down machine. However, embodiments described herein may be used on other weight lifting machines that employ stacks of weight plates that move as the machine is used. For instance, embodiments described herein may provide improvements to leg extension machines, shoulder press machines, bench press machines, and the like.

While preferred embodiments have been shown and described, modifications thereof can be made by one skilled in the art without departing from the scope or teachings herein. The embodiments described herein are exemplary only and are not limiting. Many variations and modifications of the system and apparatus are possible and are within the scope of the invention. For example, the relative dimensions of various parts, the materials from which the various parts are made, and other parameters can be varied. Accordingly, the scope of protection is not limited to the embodiments described herein, but is only limited by the claims that follow, the scope of which shall include all equivalents of the subject matter of the claims. 

1. A strength training apparatus including: a frame; an elongate guide member including a magnet; a weight plate including a guide bore through which the guide member is disposed that includes a magnet corresponding to the magnet of the guide member; where the magnet of the guide bore and the magnet of the guide member are oriented to produce repulsive magnetic forces between the weight plate and the guide member.
 2. The strength training apparatus of claim 1 wherein the magnet of the weight plate and the magnet of the guide bore maintain a gap between the inner surface of the guide bore and the outer surface of the guide member as the weight plate moves along the guide member.
 3. The strength training apparatus of claim 2 wherein the magnet of the guide member includes a magnetic insert disposed within a recess provided in the outer surface of the guide member.
 4. The strength training apparatus of claim 3 wherein the magnet of the guide bore includes a magnetic insert disposed within a recess provided in the outer surface of the guide member.
 5. The strength training apparatus of claim 2 wherein: the guide member includes a plurality of magnetic inserts, each magnetic insert disposed in a recess provided in the outer surface of the guide member; the weight plate includes a plurality of magnetic inserts, each magnetic insert disposed in a recess provided in the inner surface of the guide bore; each magnetic insert of the guide member is positioned opposite one of the magnetic inserts of the guide bore; and the magnetic inserts in the guide member are oriented to repel the magnetic inserts in the guide bore.
 6. The strength training apparatus of claim 2 wherein the entire outer surface of the guide member includes a magnet.
 7. The strength training apparatus of claim 6 wherein the entire inner surface of the guide bore includes a magnet.
 8. The strength training apparatus of claim 6 wherein the guide member is made from a magnetic material.
 9. The strength training apparatus of claim 8 wherein the weight plate is made from a magnetic material.
 10. The strength training apparatus of claim 2 further including a plurality of guide members and a plurality of guide bores through the weight plate, each guide member disposed in one of the guide bores.
 11. A strength training apparatus including: a weight plate including a magnet; an elongate guide member disposed adjacent and spaced apart from the weight plate and including a weight plate facing surface including a magnet corresponding to the magnet of the weight plate; where the magnet of the guide member and the magnet of the weight plate are oriented to produce repulsive magnetic forces between the weight plate and the guide member to maintain the gap therebetween.
 12. The strength training apparatus of claim 11 wherein the magnet of the guide member includes a magnetic insert disposed within a recess provided in the weight plate facing surface of the guide member.
 13. The strength training apparatus of claim 12 wherein the magnet of the weight plate includes a magnetic insert disposed within a recess provided in the outer surface of the weight plate.
 14. The strength training apparatus of claim 13 wherein: the guide member includes a plurality of magnetic inserts, each magnetic insert disposed in a recess provided in the weight plate facing surface of the guide member; the weight plate includes a plurality of magnetic inserts, each magnetic insert disposed in a recess provided in the outer surface of the weight plate; each magnetic insert of the guide member is positioned opposite one of the magnetic inserts of the weight plate; and the magnetic inserts in the guide member are oriented to repel the magnetic inserts in the guide bore.
 15. The strength training apparatus of claim 14 including a plurality of guide members and wherein the weight plate is rectangular and one of the guide members is positioned at each corner of the weight plate.
 16. The strength training apparatus of claim 15 wherein each guide member has an L-shaped cross section disposed about one of the corners of the weight plate.
 17. The strength training apparatus of claim 6 wherein the guide member is made from a magnetic material.
 18. A method for guiding the movement of a weight plate of a weight training machine including: positioning an elongate guide member adjacent the weight plate; creating a gap between the guide member and the weight plate; and generating a repulsive magnetic force between the guide member and the weight plate.
 19. The method of claim 18 further including moving the weight plate relative to the guide member and substantially maintaining the gap between the guide member and the weight plate by using the repulsive magnetic force.
 20. The method of claim 19 further including positioning the guide member through a guide bore provided in the weight plate. 